Structure-Function Relations in the Leaves of Maize and Barley: Sink-to-Source Conversion

[9320218] Evert本次拟开展的研究包括利用明场显微镜、透射电子显微镜、荧光显微镜和共聚焦激光扫描显微镜对玉米和大麦叶片的发育和结构进行研究。发育和结构研究将以实验研究为补充，旨在确定：1)光同化物在源和汇叶片中所遵循的途径；2)源叶和汇叶韧皮部分别加载和卸载的位置和机制；3)与汇源转换相关的结构改造；(4)水分通过蒸腾流进入叶片，经过不同层次的中脉、小脉和横脉进行汇源转换的途径。玉米和大麦和其他禾草叶片一样，提供了一个很好的系统，可以精确地跟踪细胞和亚细胞事件的序列，因为叶片基部的极化细胞分裂导致细胞发育的未混合梯度。这个相同的系统对于确定汇源到源转换的底层机制应该是理想的。玉米和大麦的叶片在结构和发育的许多细节上都不同。对这两种具有重要经济价值的禾本科植物的叶片进行平行研究，将比只研究其中一种禾本科植物的叶片结构-功能关系提供一个更平衡的图景。这些研究的结果将对作物生产力具有长期的实际重要性，并将对研究病毒、昆虫、支原体和其他寄生虫与宿主的关系以及杀虫剂和生长调节物质在栽培植物中的运动感兴趣的研究人员有价值。＊＊＊

9320218 Evert The proposed research involves studies on the development and structure of the leaves of maize and barley, utilizing bright- field, transmission electron, epifluorescence, and confocal laser scanning microscopy. The developmental and structural studies will be complemented by experimental studies aimed at determining: 1) the pathways followed by photoassimilates in source and sink leaves; 2) the sites and mechanisms of phloem loading and unloading in source and sink leaves, respectively; 3) the structural modifications associated with the sink-to-source conversion; and 4) the pathways followed by water, which enters the leaf in the transpiration stream, to intermediate, small, and transverse veins at various levels of leaves undergoing sink-to-source conversion. Maize and barley, as other grass leaves, provide an excellent system for following a sequence of cellular and subcellular events precisely because polarized cell division at the base of the leaf results in an unmixed gradient of cell development. This same system should be ideal for determining the underlying mechanisms of the sink-to-source transition. The leaves of maize and barley differ in many details both structurally and developmentally. Parallel studies on the leaves of both of these economically important grasses will provide a more balanced picture of structure-function relations in grass leaves than would an investigation of only one of them. The results of these studies will have long-term practical importance in relation to crop productivity and will be of value to investigators interested in relations of viruses, insects, mycoplasmas, and other parasites to their hosts and in the movement of insecticides and growth regulating substances in cultivated plants. ***